l dodgson



F. L. DODGSON.

. AUTOMATIC TRAIN CONTROL SYSTEM.

APPLICATION FILED rmza. 1911.

1,416,622. Patented May 16, 19 22.

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W W W W' 1 ml/mron F. L. uonesow. AUTOMATIC TRAIN CONTROL SYSTEM.

APPUCATION FILED FEB. 23. 1 91?- Patented May 16, 1922.

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F. 'L. uouesom. AUTOMATIC TRAIN CONTROL SYSTEM.

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FRANK L. DODGSON, OF ROCHESTER, NEW YORK, ASSIGNOR TO GENERAL RAILWAY SIGNAL COMPANY, OF GATES, NEW YORK, A CORPORATION OF NEW YORK.

AUTOMATIC TRAIN-CONTROL SYSTEM.

Specification of Letters Patent.

Patented May 16, 1922.

Application filed February 23, 1917. Serial No. 150,499.

To all whom 2'25 main concern:

Be it known that I, FRANK L. DODGSON, a citizen of the Jni'ted States, and resident of the city of Rochester, in the county of Monroe and State of New York, have invented a new and useful Automatic Train- (lontrol System, of which the following is a specification.

This invention relates to automatic train control systems, and more particularly to systems of the type generally termed speed control systems.

One of the principal objects of this invention is to provide automatic means for governing railway trains so that these trains may be permitted to approach close together with safety.

A further object of the invention is to provide a system for automatically controlling the movement of a train not only in accordance with the speed at which that train is traveling and the space interval separating it from another train ahead, but also in accordance with the speed of the train ahead, thereby facilitating the movement of trains by permitting them to travel. with safety separated by a short space.

Other objects and advantages will appear more fully hereinafter as the description of the invention progresses, and the novel features of invention will be pointed out in the claims.

In describing the invention in detail, ref

erence is made to the accompanying drawings in which are illustrated preferred embodiments of the invention, and in which like reference characters refer to like parts drum constituting a part of the timing app aratus And Fig. 5 is a diagrammatic View show-- ing one form of a car-carried apparatus suitable for working in conjunction with the trackway circuits shown in Fig. 1.

Referring to Fig. 1, the numerals l and 9. designate the track rails of the usual railway track over which traiiio normally moves from left to right in the direction indicated by the arrow X. The stretch of track is divided into short sections A, B, C, etc., by means of insulating joints 3 interposed at intervals in the track rail 1. The various devices and electrical connections associated with the several track sections are the same, and for convenience these devices and electrical connections are given corresponding reference characters with distinctive exponents added. Associated with each track section is a track battery 4 which is connected across the track rails 1 and 2 at one end of that section; and connected across the track rails 1 and 2 at the other end of the corresponding section is a track relay 5 of any well known or suit able construction which is provided with contact fingers or armatures shown conventionally in Fig. 1..

Extending along the track is a continuous ramp or contact rail R which is separated by suitable insulating joints 6 into sections RA, RB. etc., corresponding in length to the track sections. Associated with each track section is a suitable source of electrical energy capable of delivering difi'erent voltages, this source being shown in Fig. 1 as a trans former T, the primaries of the several transformers being connected to the line Wires 7 and 8 which are supplied with current from a suitable alternating current generator 9. The various electrical connections between the secondaries of said transformers and the track rails and sections of the contact rails will be pointed out more fully hereinafter in the description of the operation.

Associated with each of the track sections is a timing apparatus TA which is shown more in detail in Fig. 2. The timing apparatus for only one track section is shown in Fig. 1, the others being indicated as dotted rectangles. As illustrated, this timing apparatus comprises a shaft 10 supported in suitable bearings 11 and having fixed thereto a drum 0 of suitable i sulating material. The drum 0 is provided with appropriate metallic contact strips, as 12, which are ar ranged to cooperate with a plurality of contact fingers, as 13, astened to a suitable fixed insulating support 14-. Connected to one end of the shaft 10 is a gear 15 which is driven by means of intermediate gears 16, 17 and 18 from a shaft 19 which, is connected to a motor M having an armature 20 and a field 21. The motor M is constructed or controlled in some suitable manner so as to have a substantially constant speed when supplied with energy; and since various expedients capable of causing the motor to have a substantially constant speed are well known in the art, it is unnecessary to point out this feature of the invention in detail. Secured to the shaft 10 near its other end is a pulley 22 on which is wound a suitable cordor other flexible element 23, which is connected to a weight 24. The pulley, cord and weight are shown as a simplified form of a means suitable for exerting a constant tendency to turn the shaft 10 in a clockwise direction; but it is apparent that other devices for accomplishing the same purpose may be used. Secured to the shaft 10 is a ratchet wheel 25 which carries a fixed projecting arm 26 arranged to engage a fixed stop 27 so as to limit the rotation of the shaft 10 in a clockwise direction. A pivoted pawl. 28 is arranged to cooperate with the teeth of the ratchet wheel 25, this pawl being shown as provided with a weighted end which constitutes the armature 29 of an electromagnet 30 and which tends to throw the pawl out of engagement with said teeth, the movement of the pawl under the influence of its weighted, end being limited by a suitable stop 31. Associated with the parts of the timing apparatus TA. hereinbefore described is a relay 32 of suitable construction in this instance capable of responding to alternating current. The various electrical connections shown in Fig. 2 will not be described in detail since the operation of the timing apparatus, including the various v electrical circuits established during this operation will be explained hereinafter.

Referring to Fig. 1 and more particularly to the section RA of the contact rail assoc'iated with the track section A assume that no trains are present on the stretch of track illustrated. Also, for the moment disregard the action of the difl'erent timing apparatus and assume each is in its normal position, so that the connections established by the con-- tact fingers and contact strips associated with its drum are as indicated in Fig. 1. Under these conditions a difference of potential is established between the contact rail section RA and the track rail 2 by a circuit which may be traced as follows: Commencing at the contact rail section RA, conductor 33 armature 34. of the track relay 5 in its upper position, conductor 35 conductor 4-1 armature 42 of the track relay 5 in its upper position, conductor 13 0011- ductor 4:9 aunature 50 of the track relay 5 in its upper position, conductors 51 and 52 secondary of the transformer T and conductor 53 back to the track rail 2. The voltage supplied to the contact rail. section RA by the circuit just traced is equal to the entire voltage of the secondary of the transformer T and for convenience this voltage will hereinafter be referred to as high voltage.

Assuming that a train occupies the track section D it will be readily apparent to those skilled in the art of railway signaling that the track relay 5 will be shunted or deenergized and its armatures or contact fingers will assume their lower position. WVith the armature 50 in its lower position the circuit hereinbefore traced is interrupted and a signal circuit including the conductor 55 instead of the conductors 51 and 52 is established; and since the, conductor 55 is connected to the intermediate tap of the secondary of the transformer T the voltage supplied to the contact rail section RA is lower than formerly supplied when the track section D was not occupied, this lower voltage being conveniently termed medium voltage.

Assuming that the track section (l is occu- 100 pied, the armatures of the track relay being in their lower position, the contact rail section ltri. is then connected by means of conductor to another intermediate tap of the transformer, so that a still further re- 105 duced voltage is applied to said contact rail section this voltage being conveniently termed low voltage.

Assuming that the track section B is occupied, it can be seen that no voltage will be 110 supplied to the contactrail section by reason of the fact that the armature al of the track relay 5 will be in its lower position.

From the foregoing it can be seen that the ."oltage supplied to a contact rail section associated with a given track circuit section is dependent upon the number of unoccupied track circuit sections in advance thereof. in the particular arrangement shown in liig. 1, the lengths of track circuit sections are made substantially equal to one-third of the braking distance for the particular por tion of the railway track at which these track circuit sections are located. F or eX- ample, the length of the track sections A, B and C is equal to the braking distance, so that with a train standing in the track section I), a following train entering the track section Bi will have suitiicient distance to be brought to a stop by an application of its brakes before reaching the entrance to th track section D. It is obvious, however, that the particular length of the track sections, and the number of voltages applied to the contact rail sections may be varied as desired and as best adapted to the nurticular conditions under consideration.

The voltages applied to the contact rail section associated with the track section A as hereinbe'i ore explained are these existing in case the train, assumed to be occupying successively the track sections D, C and B, is standing still or tlfitielll'lg at a very low speed, and this does not apply, as will be e;\i plained hereinafter, to cases where the i'or ward train is traveling at a comparzzitjively high rate of speed; but prior to explainii g the operation of the system when the ioiward train is traveling at a coinparatively high speed, it is considered expedient to tie scribe the construction and operation ot the car-czitrried app-ratus shown in llig. 5 so to make it clear how the variation in the voltage applied to the contact rail sections causes the proper control in the movement of the following train.

Referring to Fig. 5, the train is diagrammatically shown as comprising a pair oi. wheels 60 and an axle G1, and is illustrated as carrying a suitable form of contact shoe S adapted to make electrical cont-act with the contact rail sections BA, BB, etc. For simplicity, instead of illustiatims the trackway circuits they are shown in Fig. 1, a switch 62 :is shown. as arranged to connect t1 2, track rail 2 with taps ot the secondary of a transformer T, corresponding to hi gh, medium and low voltages hereinbe'liorc referred to. The contact shoe S is connected by conductor (33 to one terminal. of a solenoid. (34;; and. the other tern'iinal oi this solenoid 6 1i; is connected by a coinluctoi. (S5 to the frame or axle 61 oil. the vehicle, so that when the vehicle is traveling over the track an electrical connection is established between said other terminal of the solenoid and the track rail 2. The core of the solenoid (it is connected by a link 67 to a lever (58 having a curved contact portion 69 at its end; and a constant tendency to move the core 66 out otthe solenoid 6-1 is exerted by a spring 70, one end oi which is ancl'iored in any suitable way, and the other end. of which is connected to the link (37. The n'iovement of the lever 68 limited by a suitable stop 7 1. Associated with the core 66 ot the solenoid 6% is a time element device For limiting; the rate oi? upward movement of sanl core. this device being shown conventionally as co? prising a piston having; a flexible p: in movable in a cylinder 58 having a reb7 stricted inlet port in its lower end.

The car-carried apparatus includes a suitable iorm of speed-responsive device 9 capable of indicating or establishing, by the movement given to a part, the actual speed at which the vehicle is traveling at that instant. in the diagrammatic illustration of the invention shown in. F :3, this speed respo sive device comprises weighted arms 7 pivotally connected to a collar 73 which is mounted on a sqi'lared. portion of a shaft 74; so as to turn therewith but so to be capable of sliding; lengthwise thereon, the shaft 74. bcilig' driven from the axle 6]. by means oil meshing beveled gears 7 5 and 7 6. Another collar 77 fixed to the shaft 74 is pivotally connected to links 7 8 which are also coni'iected to intermediate points oi the weighted arms 72. A compression. coil spring 79 is interposed between the collars 73 and 77. Located adjacent to the speedresponsive device (l is a lever 80 having a curved contact piece 8]. at one end and connected at its other end by means of a aw 82 and pin with a collar loose on the shaft Arranged to contact with the curved contact pieces of the levers 68 and 80 are a plurality oi contact springs 84; which are connected in pairs by a plurality o'l conductors 85.

The auton'iatic train control apparatus is sliown as capable of controlling; the movement oi? the train by automatically causing an application of the brakes when necessary, although it is obvious that additional operations, such as shutting oil the power may be also accomplisliied if desired. The particular embodiment of the invention illustrated in ll 5 is shown as applied to the well known system of air brakes comprising a train pipe 86 which is connected to a. suitable valve 87, it being," understood by those skilled in. the art that the opening oi? the valve 87 causes a venting ot the train pipe and results in an automatic application oil. the brakes. Arranged near the valve 87 is a brake controlling solenoid 88 having; a vertically movable core 89, in which is lined a pin 90 adapted to strike the arm 91. of the valve 87 and cause an. opening of said valve when the core 89 assumes its lowermost position. To the lower end of the core is secured a piston 92 having a flexible iiaiixking, and the piston 92 fits in cylinder 93 having' a restricted. exhaust orifice 94- in its lower end. It will be apparent that when the solenoid 8S ceencrgized, its core 89 and the piston 92 will move downward due to their wekrht slowly in accordance with the rate at which air escapes through the orilice 94;, but ii the solenoid. is reeiicrgisied. its core 89 I be quickly returned to its 'tllflWl'lllOSl; position. in general, the solenoid S8 and its associated parts constitutes a means for operatino' the brake valve 87 alter the lapse of a predetermined time following the deenergiration of the said solenoid.

There is preferably associated with the 'rain control apparatus a warning signal his shown in Fig. as follows: it hen whici is shown as an. air operated whistle l The operation of the whistle W is co11- trolled by a solenoid 95 .which operates a valve 96 contained in a suitable casing 97.

When the solenoid is deene ed the valve 96 moved by its own weight to its lower position where communication is established from a suitable source of compressed air such as the main reservoir 98 on the train through a pipe 99, valve casing 97, and DZLSSttgG 100 to the whistle lV, thereby causing; an immediate sounding of the whistle upon deenergization of the solenoid. The solenoid 95 controlling the whistle W and the solenoid 88 controlling the brake valve 87 are included in series in a circuit. including a suitable source oil? current as ahattery 1.01, conductors 102, 103, 104i: and 105, which terminates at the levers and 80. Between the levers 68 and 8 the circuit for said solenoids includes one or more oil. the conductors The car apparatus shown and described is m rely typical of: the kind of the car equipment which may be employed. in. accordance with my invention; and the detail construction and operation of this apparatus by itself in general forms no part of my present invention, being disclosed and claimed in other applications.

The operation of the car-carried app rm e switch. 62 is in the position showm high voltage is applied to the contact rail section by a circuit tram-ed as iollows: connnencinc at the contact rail section ltd, conductor 1G5, secondary oi translormer ll, conductor 10?, switch 62 and conductor i108 to the track rail 2. Thus sullicient cu: t is slniplied to the solenoid ti l so as to i'novc its core 66 against the opposition ol the spring 70 to the point where the lever (it; is in its upper; most posiliorn as showin where its (Jll".."v'(itl contact portion (39 is in cor. t r with each. oi

the contact springs 84-. al the lever it;

in this position, it can be seen that the lover 8U operated by the speed-responsia'c device G may be moved to its uppernuist position (indit l lines) without interruptn the one" trough the solenoids-i 95 and 88 controlling); the warning signal l l and the brake valve *7. respectivel v. lV hen the switch is nursed to an ;li. te position, so as to apply a lower voltage to the contact rail. section ltd, less current Elem; through the solenoid (54., so that the spring; 70 moves the core ('36 upward to an in! mediate position, degendinp; upon the age applied to the contact rail section.

smiling that is voltage is medium vol the spring ll) will more the lever :38 to t point where it makes con it with all h contact springs 8st except the uppermost coin tact spring. 'l hen in order to prevent an interruption oi the circuit through the solenoids 88 and 95 it is necessary for curved contact portion 81 of the lever operated by the speed-responsive device G to move to an' intermediate position in which it makes contact with the middle contact spring 8 h In the same way when low voltage is applied to the contact rail section the speed of the vehicle must be further reduced.

in general, the solenoid (34; together with its associated nnts constitutes a means for establishing a permissive speed for the vehicle in accordimce with the voltage applied to the contact rail sections. ll the actual speed oi the vehicle which is indicated by the speed responsive device G, exceeds the )ermissive speed the circuit for energizing; he solenoids 88 and 95 is interru ated, and the warning signal i is immediately sounded. and. the core 89 oi the brake eontroh ding solenoid 88 commences to move downward. It is contemplated that the engineer or motorman ot the train, upon the sounding or the warning signal U, will immediately sh at oil the power and apply the brakes; and the appznatns is preferably so arranged that when the ca rineer or motorinan obeys the varning signal. in this way, he will. be able to cause sullicient reduction in the speed of the vehicle as to re-estahlish the circuit through the con"?olling solenoid 88 prior to the lapse of time for which the dasltpot d vice is adjusted. In other words, the system is pielerably so constructed that the engineer or motorman, by promptly obeying the warning signal, lV, may avoid an automatic application of the brakes. .ln this connection suitable recording or regisinp; devices .ruay be used. in conjunction th the brake controlling; solenoid 88 so as are well known in described in detail. hetrring now to .ll'ig, 1, assume that a train equip nzd with the apparatus shown in l 5 enters the tract: section A when unyer train is standing in the track section t can be seen that the :lollowing train .i cn'ielled. automatically to reduce its speet as it moves throruzh the sliiccessive tract: sections B. U and l) toward the forward train, by re son of the limit that the sru-ressive contact rail sections RA, BB RC are supplied with successively lower voltrs, as previously explained; and the sucsi rediurtionsin speed compelled by the ,omntic appznfatus selected. with a view at bringing the following train to a stop to a predetermined low speed by the time it reaches the end oi the block C.

it may well happen that when a train ap proaches so cl se to a train ahead as to make it desirable to retard. the following train, the 'lorward train will be traveling at a com pa 'atively high rate of speed so that, even it it were to innnediately apply its hrakes it would travel considerable distance. Thus, if it is taken into consideration. that the for ward. train is traveling at a comparatively high. speed and cannot under the worst conditions be brought to a stop for a considerable distance, it can be seen that the following train may approach closer to the forward train with proper safety than would be the case if the forward train were standing still. In other words, if the relative braking distances of two trains is made the determining factor of whether or not an automatic governing of the following train should occur, the physical space interval between the two trains may be materially reduced; and one of the important features of this invention is its capability of making the speed of the forward train one of the determining factors in the automatic control of the following train. In the particular embodiment of the invention illustrated the speed of the forward train is determined by ascertaining the time taken by said train to travel a predetermined distance. In accomplishing this purpose it is desired to use as much as possible the parts of the trackway circuits which are necessarily used. in order to afford the proper control of the train when the forward train is standing still, and according to the embodiment of the invention illustrated, the time is measured from the time the rear end of a train leaves a given track section until it leaves the next track section in advance.

Referring to Fig. 2, assume that a train, traveling from left to right in the normal direction of tra'liic, enters the track section B, progresses int the track section C and finally entirely leaves the track section B. At the instant when the rear end of the train leaves the track section B the track relay 5 is reenergized and its armature 109 raised so that a circuit for energizing the relay 32 is established as follows: commencing at one terminal of the secondary of transformer 1 conductors 111, 112 and 113, armature 109 of the track relay 5 in its upper position, conductor 114i, armature 110 of the track relay 5" in its lower position, conductors 115 and 116, contact finger 117 contact strip 118, contact finger 119, conductors and 121, relay 32 and conductors 1.22. 123 and 124 back to the other terminal of the secondary of said transformer.

Referring to Fig. it can be seen that the contact strip 118 is of such a length and so arranged that after a slight movement of the drum O the electrical connection be tween the contact fingers 117 and 119 is broken, the purpose of this arrangement be ing pointed out hereinafter. When the relay 32 is energized and its armature 126 raised, a shunt is established around the contact fingers 117 and 119 comprising conductor 125, armature 126 of said relay in.

its upper position and conductor 127, so that after the relay 32 is once energized, and although its energizing circuit is immedi ately interrupted by the movement of the drum, the relay 32 is maintained energized by its maintaining or stick circuit until the armature 110 of the track relay 5 resumes its upper position due to the movement of the train entirely outv of the track section C.. The raising of the armature 128 of the relay 32 closes a circuit for supplying energy to the motor M, said circuit being traced as follows: commencing at one terminal. of the secondary of the transformer t, conductors 1.11, 112 and 129, contact finger 130, contact strip 12, contact finger 13, conductor 131.armature 20 of the motor M, field 21 of said motor, conductor 132, armature 128 of the relay 32 in its upper position and conductors 133 and 124: back to the secondary of said transformer. The motor 1W1 gradually turns the shaft 10 in a counterclockwise direction against the opposition of the weight 24.- at a rate corresponding to time. As the train progresses and its head end enters the track section D, the armature 136 of the track relay 5 assumes its lower position and energizes the electromagnet 30 by a circuit traced as follows: commencing at one terminal of the transformer t, conductors 111 and 13 1, elcctromagnet 30, conductor 135, armature 136 of the track relay 5 in its lower position, and conductors 137 123 and 121- back to the other terminal of the secondary of said transfm'mcr. The energizing of the clectromagnet 30 moves the pawl 28 into position to engage with the teeth of the ratchet wheel 25, but does not inter tere with further movement of the shaft 10 and the contact drum. 0 by the motor M. As the train progresses and entirely leaves the track section C, the track relay 5 is again energized and its armature 110 is raised so as to interrupt the stick circuit through the relay 32, thereby stopping the motor M. The contact drum 0 will be held in the position into which it has been moved by the action of the pawl 28. so long as the train remains in. the track section D. When the train leaves track section D, the electromagnet 30 becomes deenergiaed, the pawl 28 disengages from the teeth of the ratchet wheel 25, and the shaft 10 and contact drum O are returned to their normal or initial position by the weight 24. From the foregoing, it can be seen that the position assumed by the shaft 10 and contact drum 0 becomes a measure or indication of the speed of the train while passing over the corresponding track section.

Referring particularly to the track section C, suppose that the speed of the train, determined by the time taken it to pass over the track section C is such that the train cannot even by an immediate application of its brakes be brought to a stop until its rear end has traveled beyond the track section D. l i ith such conditions existing it can be seen that it is permissible to increase the voltage applied to the contact rail sections RA and RB associated with. the track sections A and B in the rear thereof to the voltage which would. ordinarily be applied to these contact rail sections if the forward train were standing in the track section E, that is, just the same as if the train had already passed over the track section D. Likewise, if the speed or the train, indicated by the time taken it to travel. over the track section C, is so great that said train cannot be brought to a stop by its brakes until after its rear end has passed beyond the track section E, it can be seen that the voltage applied to the contact rail sections BA and RB associated with the track sections A and B may be still further increased with safety; that is, if the forward train cannot be stopped until it has passed over the track sections D and E, it is permissible to permit the following train to run at the same speed as if the track sections D and E were as a matter of fact not occupied. This change in the voltage is produced by changing the connections between the contact rail sections and the respective sources of current to which they would ordinarily be connected in accordance with the position of the armatures of the track relays, and this change in connectionis produced by the n'iovement of the contact drum 0. Beferring to Figs. 3 and 4, Fig. 3 illustrates the connection to be established under nor mal. conditions when the forward train is standing still. Fig. 3 illustrates the connections which should be established when the forward train is traveling at a high speed, that is, when it consumes a short time in traveling over the length of a track section, and Fig. 3 illustrates the connection which should be made when the forward train is traveling at medium speed. Fig. 4- illustrates the development of the contact drum O and the inter-connections between the several contact strips thereon necessary to ob tain the connections in the parts of Fig. 3, the contact drum being rotated in a direction such that in its developed form shown in Fig. 4- it moves from right to left under the contact springs.

Referring to Fig. 1, assume that the forward train travels over the track section C in such a short time that it is assured that it could not come to a stop until after passing over the track sections D and E. The timing apparatus will be operated as hereinbefore described but the contact drum 0 will only be moved a very short distance during this short time, that is, to thefirst position shown in Fig. 4, in which the connections shown in Fig. 3 are established, With these connections estab ished, high Voltage is applied to contact rail section BB associated with the track section B and also high voltage is applied to contact rail section BA. The circuit for the contact rail section BA of the track section A may be traced as follows: commencing at the contact rail section BA, conductor 33 armature 34 of the track relay 5 in its upper position, conductor 85 conductor 41 armature 42 of the track relay 5 in its upper position, conductor then referring to Fig.4, remembering that the contact drum 0 is now in its first position, contact finger 44, contact strip 144-. connector 143, contact strip 142, contact finger 140 conductors 141 and 52 secondary of the transformer T and conductor 53 to the track rail 2. The circuit for the contact rail section of the track circuit section B may be traced as follows: commencing at the contact rail section RB, conductor 33 armature 34 of the track relay 5 in its upper position, conductor 35 then referring to Fig. 4 and remembering that the contact drum 0 is in the first position, contact finger 36, contact strip 144, connector 143, contact strip 142, contact finger 14-0, conductors 141 and 52, secondary of the transformer T and conductor 53 to the track rail 2. Since thereis high voltage applied to the contact rail sections RA and BB, the following train will be permitted to proceed at high speed through the track sections A and B just as if the'three track sections C, D and E ahead were not occupied; whereas without the timing apparatus, the following train would have to reduce its speed in traveling through the track sections A and. B so long as the forward train remained in the track section D.

In a similar way, if the fmrward. train is traveling at such a speed that it must necessarily pass beyond the track section D before it can be brought to a stop, the contact drum 0 is moved to a further or second position in. which the connections are established as shown in Fig. 3 With these connections established, high voltage is applied to the contact rail section RA associated with the track section A and medium oltage is applied to the contact rail section associated with the track section B. The circuits for the contact rail sections and RB may be easily traced from analogy to those already traced, it being remembered that the contact drum 0 is now in its second position (see Fig. 4) so that a connection is established between conductors 35 and 49 by contact strips 145 and 147 and connector 146, while the connection between conductor 43. and 49 is continued by the extended contact strips 144 and 142.

It should be noted that the contact drum 0 isbeing rotated to its new position only while the train occupies the corresponding track section, as the track section C, and

that during th s time the presence olthe train on this track section jlisconuec i the condi'ictors leading to the (ll'lllll, as the con ductors 35 and 4-3", by reason of the fact that the tllllllltlll'QS as 3 1- and lil oil? its track are in the lo We]: position. In this way, the connections established by the position to which the drum 0 is moved are not capable of being etlect' until it been eterinined to whet position the drum sh old he moved according to the speed of the forward train. It should also he noted that site"? the drum 0 has once been H1OXV position and is held in that position l action of the pawl 28 and electroinagif it cannot be moved to any other p sition until it has again resumed its initial or normal position. This is due to the ope of the contact fingers 117 and 119 which interrupt the circuit for initially ene the relay 32 soon as the drinn O has corn menced its movement. l l heiii the time taken for the train to travel over the psrticnlzn track section has elapsed, the stick circuit for the relay 32 broken at the armature 110 of the track relay, and hence be oii'e it 15 possible to again energize the rclav E123 l supply power to the motor M, it is neces f for thecontact drum 0 to return to its ini tial position and again establish an electrical connection between the contact fingers 117 and 119 so as to peii'init the relay 32 to he again initially energized.

In case the train in the track section (l is standing still, or is lllftifirlllff at ich ii low speed tl'iat it might be ln'oufrht to a stop lr-v an application cl its lwalccs hei'oro entirely leaving said t'i'aclc section (3, the time during); which the liming apparatus h scion; open alierl is so great tha it the contract drum 0 is moved. substantially a toll revolution to the third position shown in Fig. 1-. in which the electrical connections established between the respective contact lingers 3th 44. ll and 418 are the same as are estal'ilished in the normal or initial position the drum, in other words when the iorwa d t standing still or traveling a. lo the voltages applied to the tions of th tra V sect-i no the a i timing an the, the. is, the apparatiis z'zssoi'ziziltod with each track section constiti'itcs a means for varying the control applied to a jl ollowin g train according to the speed, of the 'lioiwawl train. :he particular place where the track section in (g'iiestion loi'zateil, so that to? all parts of the stretch of railway equipped with the automat c train control s' ein embodying this invention trains are llllltljfll to run at a i or d'stani'te apart dependii upon their relative in. hing; o scipientlv the system einbodving this ll lTGllti n enables trains =10 be spaced closer to- .1 her with proper satety and in this wr enables a greater cility of movement oi the trail The described inclndi the may be applied to the entire length or Jailwo 01: any pa'ticilar sections or portions thereof, as may he desir It is also contei'nplatcd that spe rial con ions may make it des'rable to use system witli the timing api mretns tor FlOHM parts or ctions of the railway while for other par o't tl c railway it wi not be no 1 to use the timing apparatus in the system.

From the foregoing it can be seen that in accordance with this invention provisions are inane su h that when a train is standing still on portion oi the railway track, its presence is detected, and a manifestation of its prose appears as varying; voltages applied to several, contact rails throiiqhoiit a zone in the lQitl oil slid train, the extent or length o!" his moo being; dctci'ini'neil, by the dis lice i'coiiii'cil ilor a 'l ollowii'ip; ti'aii'i to he brown I- to a stop or to a Pl'EflGlTCl'll'illlOd low Hp ed, p i ./\lso" ii the forward b1 an :rp 'ilication oi its brakes.

d the torwz, 1 .rain. he con v,ct rails id contact shoes which are made a, pain if rticular eo'ibodinient oi the in ntion in. ol a means adapted to establish communicot'ion between a moving; train and iniipiili te devices along the track; but it is to be illfllll'ly understood that 1 contemplate as ia-lli within the scope of my invention other forms of communicating devices, the different controlling conditions of said cominunicatin devices being produced by variations in the voltage applied thereto or by other expedients in accordance with the pan ticular character of the communicating means.

Various modifications and applications of the system embodying this invention, other than those illustrated and described. and which utilize the important and. desirable features of this invention, will be readily apparent to those skilled in the art of railway signaling after acquiring a thorough knowledge of the invention. Among such changes and modifications, the speed control apparatus responding to the varying controlling conditions, namely the varying voltages applied to the several contact rail sections, may take other forms than the specific type of apparatus illustrated and described; and in the same way other arrange ments of traclrway circuits, involving the same principles of operation, might be used. The particular embodiment of the invention selected to illustrate the principles of operation and important features of the invention, has been illustrated and described with special reference to double track railways in which trains normally run in one direction on each track; but it wish it to be clearly understood that l contemplate the application of my invention to single track railways and to other special cases. Consequently, although I have particularly described the construction of one physical embodiment of my invention, and explained the ope ation. and principle thereof; neverthe- I desire to have it understood. that the torm selected is merely illustrative, but does not exhaust the possible physical embodiments oi? the idea of means underlying my invention.

What I claim as new and desire to secure by Letters Patent of the United States, is:

1. In an automatic train control system, in combination: a railway track; traclrway means responsive to the presence of a train on said track for creating a zone 01" variable in fluence extending in the rear of said train for a distance corresponding approximately with braking distance for the trains" means controlled the speed of said train for varying the length of said Zone; and means on the following train responsive to the iiifluence of said zone for limiting its speed in accordance with its location. in said some.

In an automatic train control system, in combination: a railway track; conu'nunieating means along the track for communieating to trains thereon; means responsive to the presence of a train on said track and its speed for establishing varying controlling conditions of said means at different points in the rear of said train throughout a zone of limited extent; the controlling conditions of said communicating means at the ditlj erent points in said zone being dependent upon the distance between that point and the pointwhere said train may be brought to a stop by the action of its brakes; means on a :lollowing train responsive to the varying controlling condition of said. communicating means tor limiting the speed ol said following train.

3. in an automatic train. control system, in combination: a railway track; impulse devices along said track adapted to have dill'erent controlling conditions; traclrway means responsive to the presence of a train on said track and. its speed for establishing (lit pulse levices in the rear thereoi throughout a Zone of limited extent which has its length dependent upon the speed of said train; and means on a following train controlled by said impulse devices for imposing a limitation upon the speed of said following train in accordance with the controlling condition of said impulse devices.

w nt controlling conditions of the im-' l. In an automatic train control system tor railr ads having tracks divided into track sections each provided with a track relay, speed control apparatus on a vehicle comprising a permissive speed element Inovable to different positions in accordance with the intensity of electrical energy supplied thereto, an actual speed device assuming different positions in accordance with the actual. speed of the vehicle, brake setting means controlled jointly by said permissive speed element and said actual speed device,

and traclnwiy means controlled by said.

tracl'z circuits and adapted to supply electrical energy to the vehicle varying in in tensity in accori'lance with the location and speed of a train ahead.

5. In an automatic train control system, in combination: a railway track divided into track sections; an impulse device associated with each track section. and adapted to have v a gin controlling conditions means responsive to the presence of a train on each track section for giving varying controlling conditions to the impulse devices associated. with a undetermined number of track sections in the rear: means dependent on the speed. of said train through said track section for modifying the controlling conditions of said impulse devices in the rear; and means on afollowing train responsive to the varying controlling conditions of said impulse devices for regulating the speed of said following train.

6. In an automatic train control system, in combination a railway track divided into track sections eaiizh, having a track relay; a contact rail. associated with each track section means controlled by the track relay of each track section for applying different voltages to the contact rails of a predetermined number of said track sections in. the rear; means controlled by the speed of a train traveling through each track section for changing the voltages applied to the contact rails of the track sections in the rear in accordance with the speed of said train; and means on a followii'ig train responsive to the variations in the voltage applied to said contact rails for limiting the speed o't said "following train 7. In an automatic train control system, in combination: a railway track divided into track sections; impulse devices along the track adapted to have difierent controlling conditions; means responsive to the presence of a train on a track section for giving varying controlling conditions to the impulse devices for a limited distance in the rear thereof; timing apparatus associated with each, track section for determining the time taken by the rear end of a train to pass through the track section; means controlled by said timing apparatus for changing the controlling conditions of the impulse de vices in the rear of the corresponding track section in accordance with the time oi? operation of said timing apparatus; and means on a following train for limiting its speed in accordance with the controlling conditions of said impulse devices.

8. In an automatic train control system, a railroad track divided into track circuit sections, a plurality of said track sections constituting braking distance for the vehicles traveling over the track, impulse transmitting means extending throughout. the length o't each track section and effective to transmit controlling influences to a passing vehicle in accordance with the voltage applied to said impulse transmitting means, means responsive to the presence of a vehicle on said tracl: sections and its speed through such track section for supplying dit iterent voltages to the impulse transmitting means of a number of track sections in the rear thereof, and means on a following vehicle for imposing restrictions on its speed in accordance with the varying controlling influences communicated to it in the successive track sections, whereby the speed of the following vehicle will be restricted in accordance with the distance between it and the vehicle ahead and also the speed of? the vehicle ahead.

9. In an automatic train control system, a railroad track divided into tract: circuit sections, impulse transmitting means asso ciated with each track section and capable of assuming ditlerent controlling conditions time controlled apparatus associated with each track section and governed by the track circuits of that track section and the track section next in the rear, said apparatus act-- ing to vary the controlling conditions oi the impulse transmitting means of number of the track sections to a limited distance in the rear in accordance with the time taken by a vehicle to travel through the traclr section corresponding to said apparatus, and. speed control. apoaii'atus on the :l ollowing vehicle regoonsive to the varying controlling con ditions cl said impulse la-ansmitting means.

ll). in. an automatic train control. system, a railroad track divided into track circuit sections, a plu alit v o't said track circuit sec-- tions constituting braking distance for the vehicles travel'. over the track, impulse transmitting means for each track section, met ns associated with each trac I section for placing its impulse transmitting means in a predetermined mudition in accordance with the number of unoccupied track sections of said plurality in advance thereof, and means responsive to the speed o l" a vehicle in. any one oil. said phu-ality of? track sections for modifying the controllin 7 condition of said impulse transmitting means associated with the track sections in the rear, whereby the controlling condition of the impulse transmitj'ig means o'l each traclr section is automaticallv ClQ JGUL'lGHt upon the number of unoccupied track sections in advance thereof and also upon the speed ot the vehicle in the first occupied track section.

ll. in an automatic speed control system adapted to regulate the speed of vehicles in accordance with the distance to the next vehicle ahead and also the speed of said vehicle ahead, a track divided into track circuit sections, a plurality of which constitute braking distances for the vehicles, means including impulse transmitting devices "for impos-zing varying speed restrictions on a follow; 1;; vehicle in each track section in accm'dance with the number of unoccupied track sections oi" said phirality in advance therco'li, and means including time controlled apparatus adapted to determine the speed of: the vehicle in any one of said advance track sections tor modifying the action of said lirst mentioned means to permit higher speeds for the :lollowing vehicle. 7

12. In an automatic train control system, the combination with a vehicle, of a permissive speed device on the vehicle biased to assume its lowest speed condition, means partly on the vehicle and partly along the track for causing said permissive speed device to assume higher speed conditions in opposition to its bias, and means cmnpelling said permissive speed device to change slowly to its lowest speed condition in re sponse to its bias but permitting a quick change to higher speed conditions.

In automatic train control system, the combination with a vehicle, of a permissive speed device on the vehicle biased to assume its lowest speed position, electrically operable means for causing said permissive speed device to assume higher speed positions in opposition to its bias, time controlled means. for, regulating the change of said permissive speed device to its lowest speediposition, a speed responsive device establishing. the actual speed oi? the vehicle, and a safety appliance for excessive speed operated when the actual speed of the ve hicle exceeds the permissive speed prescribed by said permissive speed device.

14. In an automatic train control system, a track divided into track circuit sections, time. controlled apparatus associated with each track section and; adapted to determine theispeed of vehicles traveling through that track section, said time controlled apparatus comprising a. movable element, a motor for moving said element in accordance with time, and control means governed by the track circuits of the corresponding track section and the track section next in the rear and adaptedzto cause said motor to operate from the time a vehicle leaves the rear track section until it leaves the advance track section.

15. In an automatic train control system, a, track divided into track circuit sections, time controlled apparatus associated with each track section and adaptedto determine the speediofli'vehicles through that track section, said apparatus comprising a movable element biased to one position, a motor for moving said element from its biased position in accordance with time, control means governediby the track circuits of the corre sponding track section andthe track section next inthe rear for causing said motor to operate during the time elapsing between the successive. re-energization of said track circuits, and means controlled by the track circuit: of the track section next in advance of the track section corresponding to said apparatus for maintaining said movable element in its moved position against theiopposition ofits bias so long as saidadvanced track; section a is occupied.

16. In an automatic train control system, speed control apparatus on a vehicle including a permissive speed device biased-to its lowest speedcondition, means partly on the vehicle andpartly along the track for causing said device to assume higher speed condit'ionsin accordance with the location and speed of atrain ahead, and a brake setting applianceacting to apply the brakes auto matically. when the actual speed of the vehicleexceeds that prescribed by theexisting condition otisaid permissive speed device.

17. A speed control system for railroads divided into short track sections each hav ing a track circuit, comprising impulse de vices alongthe track adapted to assume ditt'erent controllingconditions corresponding to the safe speedlimit ior a following train, means forugoverning the controlling condition of: said impulse devices by said track circuits, and means responsive to the time pendent upon the distance to the next train ahead and the speed of that train.

18. An automatic speed control systemfor railroads divided into track sections each,

provided with a track circuit, comprising a trackwa-y impulse device associated with each track section, means responsive to the presence of a train on a given track section for causing the impulse devices of anumber of track sections in the rear thereof to. assume permissively varying controlling conditions, and means responsive to the time taken by the rear endo'f a train intraveling, through said given section for independently controlling, said impulse devices in the rear.

19. Inv an automatic train control system for railroads divided into track sections, impulse devicesassociated with said traclr sections, and means for governing groups of said devices, said means comprising time responsive means and a governing circuit therefor which includes front and back contacts of the track relays of two adjacent track sections, whereby said time responsive means is operated. while the rear end of a train is passing through the corresponding track section.

20. In an automatic train controlsystem tor railroads divided into track sections each provided with a track relay, the combination with speed controlledapparatus on a vehicle adapted to enforce varying restrictions upon the speed thereof, of trackway means controlled, by, the track relays for creating a Zone of variable influence in the rear of a train occupying a given track section, which zone of influence varies inextent, in accordance with the, time taken by that train. to pass through a track section, said zone of influence being adapted to control, the speed control. apparatus on a following;

vehicle.

21. In an automatic train controlsystem, the combination with car apparatus comprising permissive speed means responsive to electric energy ofvarying,characteristics, and brake control means operatedwhen the car exceeds a speed corresponding to that prescribed by the existing condition. of said permissivespeed means, of trackway means including a continuous conductor and sources oi electrical energy of different characteristics tor influencing said permissive speed means tea variable degree dependent upon the distance between the car and the, next train ahead and also the speed of said train ahead.

29. An automatic system for regulating the speed. otrailroad trains comprising brake governing apparatus on the train adapted to cause an automatic brake application when the train exceeds predetermined variable speed limits, said apparatus having a tendency to assume an active condition and stop the train, and automatic means for continuously influencing said apparatus and put it in a speed limiting condition dependent upon the distance to the next train ahead and the speed of that train ahead, said automatic ieans comprising a time element device antomatically controlled by said train ahead.

23. In an automatic speed control system for railroads, a changeable permissive speed means on a car biased toward its lowest speed condition, cooperating car carried means and trackway means for continuously influencing the permissive speed means to maintain it in a speed limiting condition corresponding to the extent of unoccupied track ahead of the car, and trackway means controlled by the speed of a train traveling thereby for modifying such influence upon the permissive speed means on a following car, whereby the permissive speed means on a car is regulated in accordance with the dis tance between it and the next car ahead and also the speed of said car ahead.

24. In an automatic train control system comprising a continuous conductor along the track divided into sections, a plurality of which constitutes braking distance for the trains traveling over the track, trackway means including sources of current of out ferent voltage for energizing each section of said conductor with a voltage dependent upon the distance between that section and the next train ahead and also the speed of said train ahead.

A train control system comprising means including track devices for imposing predetermined speed restrictions on passing vehicles at a plurality of control points in the braking distance thereof, and trackway means responding to the speed of trains for modifying the action of said track devices braking distance in the rear ot such train and thereb permit higher speeds for a following vehicih.

26. In an automatic train control system comprising means including track devices for automatically determining the speed limit for passing vehicles in accordance with the extent of unoccupied track in advance thereof, and trackway means influenced to a variable degree by the speed of a train for modifying the influence of the track devices throughout braking distance in the rear of that train and thereby establishing higher speed limits for a following vehicle depend ent upon the speed of said train ahead.

FRANK L. DODGSON 

